Turboprop engine with an air-oil cooler

ABSTRACT

A turboprop engine in the pod of which an air-oil cooler is disposed downstream of a cooling air inlet opening. The oil cooler exhaust air is discharged via an air duct with which a cooling air conveying device is associated. In this way it is ensured that there is always a sufficient cooling air flow and that this air flow, as a relatively cold air flow, can also cool other units in the engine pod before acting on the oil cooler.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a turboprop engine having an inlet openingprovided in the engine cage for cooling air for the cage interior andfor an air/liquid heat exchanger arranged in this interior, having acooling air delivery device as well as having an air guiding duct whichaccommodates the liquid/air heat exchanger and carries away the heatexchanger exhaust air.

Such a turboprop engine is known from U.S. Pat. No. 2,593,541. In thiscase, the air flow provided for an air oil cooler arrives directly froman inlet opening in the engine cage at the air oil cooler. The oilcooler exhaust air is carried away by way of the turbine exhaust airduct, the corresponding introduction device of the cooling air flow intothe turbine exhaust air duct being constructed in the form of an ejectorso that a cooling air delivery device is provided in the shape of thisejector. Such a cooling air delivery device is useful for thoseoperations of the turboprop engine in which an aircraft equipped withthis engine rolls along on the ground, particularly if a rolling alongin the reverse direction takes place.

Another turboprop engine having a liquid-air heat exchanger,particularly an air oil cooler, is illustrated in European PatentDocument EP 0 514 119 A1. Here, the air oil cooler is arranged in thearea of the inlet opening so that the cooling of the cage interior takesplace by means of the oil cooler exhaust air flow. In this case, the oilcooler exhaust air flows around the assemblies to be cooled which arearranged in the engine cage and is then also carried off by way of theturbine exhaust air duct, again the corresponding introduction device ofthe cooling air flow into the turbine exhaust air duct being constructedin the shape of an ejector.

At high exterior temperatures, for example, the oil cooler exhaust airflow can assume such high temperatures that the assemblies arranged inthe engine cage which are acted upon by this air flow may be damaged.

It is an object of the invention to indicate measures by which anassembly arranged in the engine cage can be reliably cooled and in theprocess a sufficiently intensive air flow is guided through theliquid/air heat exchanger.

The achieving of this object is characterized in that the cooling airinlet opening is adjoined by an air guiding duct which is directed to atleast one assembly to be cooled, and in that the cooling air deliverydevice is constructed as a fan which is disposed in front of the heatexchanger and is arranged in the air guiding duct.

In that the heat exchanger or oil cooler is arranged away from the inletopening and a cooling air delivery device is provided which isconstructed as a fan, the cooling air flow arriving through the inletopening in the cage interior can first optimally act upon the assembliesto be cooled and will only then arrive on the oil cooler. From this oilcooler, this then heated air flow is carried away as the oil coolerexhaust air flow in a targeted manner, specifically by way of an airguiding duct so that any heating of the cage interior by the oil coolerexhaust air is virtually excluded.

In order to, in the process, guide the cooling air flow, which arrivesin the engine cage by way of the inlet opening and which, because of thefan, is definitely of a sufficient intensity, in a targeted manner tothe assemblies to be cooled, the air inlet opening is adjoined by anappropriately designed air guiding duct. In this air guiding duct orgenerally at the cooling air inlet opening, a separating device forwater and/or particles, which may damage the cage interior, may also beprovided.

The cooling air delivery device constructed as a fan can be driven by anelectric motor, which has the advantage that, in a simple manner, onlyat a few operating points, specifically when a separate cooling airdelivery is required at all, the required fan power must be provided.Since, however, a corresponding electric motor also results in anincreased weight, the fan can also be driven mechanically by way of theso-called gear box, that is, by way of the transmission arrangement forthe auxiliary unit drive of the flight gas turbine known to the personskilled in the art. Here, it is recommended to arrange a shiftingcoupling between the fan as well as the corresponding gear box outputshaft in order to again only have to drive the fan if the delivery of acooling air flow is required.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal sectional view of a turboprop engineaccording to a preferred embodiment of the present invention;

FIG. 2 is a schematic longitudinal sectional view of a turboprop engineaccording to another preferred embodiment of the present invention; and

FIG. 3 is a schematic longitudinal sectional view of a turboprop engineaccording to another preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 1-3, identical structural elements have the samereference numbers.

A gas turbine arranged in the engine cage 1 has the reference number 2.By way of a transmission 3, this gas turbine 2 drives a propeller 4.Since a relatively high power is transmitted in the transmission 3, acooling of the transmission oil is required. For this purpose, an oilcooler 5 is arranged in the cage interior 6.

The oil cooler 5 or generally the air/fluid heat exchanger 5 receivesthe required cooling air by way of a cooling air inlet opening 7 whichis provided in the engine cage 1 and can be optimally constructed underfluidic aspects, for example, as illustrated in the shape of a guideblade which partially siphons off the air flow arriving on it. Thisinlet opening 7 is adjoined by an air guiding duct 8 by way of which thesiphoned-off cooling air flow is supplied to the assemblies to be cooledwhich are arranged in the engine cage 1 and are not shown in detail andgenerally have the reference number 9.

After the cooling air flow has swept over the assemblies 9, it arrivesat the oil cooler 5 and from it, as an exhaust air flow--as illustratedby arrows--by way of an air guiding duct 10 reaches the environment. Inthis case, the described guiding of the cooling air flow is provided bya cooling air delivery device which in general has the reference number11 and which is assigned to the air guiding duct 10 which--in the widestsense--accommodates the oil cooler 5.

In the embodiments according to FIGS. 1, 2, the fan or the cooling airdelivery device 11 is driven by means of a shifting coupling, which isnot shown, by the gear box 13 assigned to the gas turbine 2 and arrangedin the cage interior 6, specifically by way of an output shaft of thegear box 13.

In the embodiment according to FIG. 3, the fan or the cooling airdelivery device 11 is driven by way of an electric motor 14.

In the embodiments according to FIGS. 1, 3, the air guiding duct 10carrying away the heat exchanger exhaust air leads into the turbineexhaust air duct 12, while in the embodiment according to FIG. 2, theair guiding duct 10 for the oil cooler exhaust air leads directly intothe environment so that no undesirable influencing of the flowconditions takes place here in the turbine exhaust air duct 12.

All embodiments have in common that the cooling air flow arriving in thecage interior 6 by way of the inlet opening 7 is first guided over theassemblies 9 to be cooled and will only then reach the oil cooler 5arranged away from the inlet opening 7. From this oil cooler 5, the airflow, as oil cooler exhaust air, is then in all embodiments carried offby way of the air guiding duct 10 into the environment without anynoticeable heating of the cage interior 6 taking place. In this case,the cooling air flow is always delivered by a delivery device 11assigned to the air guiding duct 10. Naturally, a plurality of details,particularly of a constructive type, may be designed to deviate from theillustrated embodiments without leaving the content of the claims.

Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexample, and is not to be taken by way of limitation. The spirit andscope of the present invention are to be limited only by the terms ofthe appended claims.

What is claimed:
 1. A turboprop engine, comprising:an engine casingdefining an interior and defining an cooling air inlet opening into saidinterior for cooling air; a cooling air guiding duct adjoining saidinlet opening, said cooling air guiding duct being directed to at leastone assembly to be cooled; an air-liquid heat exchanger arranged in saidinterior; a cooling air delivery device arranged adjacent and upstreamof said heat exchanger and downstream of said at least one assembly tobe cooled; and an exhaust air guiding duct arranged adjacent anddownstream of said heat exchanger.
 2. A turboprop engine according toclaim 1, wherein the cooling air delivery device is a fan.
 3. Aturboprop engine according to claim 2, wherein the fan is driven by oneof an electric motor and a shifting coupling of a transmissionarrangement for an auxiliary unit drive.
 4. A turboprop engine accordingto claim 1, wherein said exhaust air guiding duct is communicated withan exhaust duct of a gas turbine.
 5. A turboprop engine according toclaim 1, wherein said exhaust air guiding duct is communicated with anambient environment.
 6. A turboprop engine according to claim 1, whereinthe cooling air delivery device is driven by an electric motor.
 7. Aturboprop engine according to claim 1, wherein the cooling air deliverydevice is driven by a shifting coupling of a transmission arrangementfor an auxiliary unit drive.
 8. A turboprop engine according to claim 1,wherein said heat exchanger is arranged rearward of said cooling airguiding duct.
 9. A turboprop engine according to claim 1, wherein saidexhaust air guiding duct is arranged rearward of said heat exchanger.10. A turboprop engine according to claim 8, wherein said exhaust airguiding duct is arranged rearward of said heat exchanger.
 11. Aturboprop engine, comprising:an engine casing defining an interior; anassembly to be cooled arranged in said interior; a cooling air guidingduct communicating said interior with an ambient atmosphere, saidcooling air guiding duct having an outlet arranged proximate saidassembly to be cooled such that said cooling air guiding duct directscooling air to said assembly to be cooled; an air-liquid heat exchangerarranged in said interior downstream of said assembly to be cooled; acooling air delivery device arranged adjacent and upstream of said heatexchanger and downstream of said at least one assembly to be cooled; andan exhaust air guiding duct arranged adjacent and downstream of saidheat exchanger.
 12. A turboprop engine according to claim 11, whereinthe cooling air delivery device is a fan.
 13. A turboprop engineaccording to claim 12, wherein the fan is driven by one of an electricmotor and a shifting coupling of a transmission arrangement for anauxiliary unit drive.
 14. A turboprop engine according to claim 11,wherein said exhaust air guiding duct is communicated with an exhaustduct of a gas turbine.
 15. A turboprop engine according to claim 11,wherein said exhaust air guiding duct is communicated with an ambientenvironment.
 16. A turboprop engine according to claim 11, wherein thecooling air delivery device is driven by an electric motor.
 17. Aturboprop engine according to claim 11, wherein the cooling air deliverydevice is driven by a shifting coupling of a transmission arrangementfor an auxiliary unit drive.
 18. A turboprop engine according to claim11, wherein said heat exchanger is arranged rearward of said cooling airguiding duct.
 19. A turboprop engine according to claim 11, wherein saidexhaust air guiding duct is arranged rearward of said heat exchanger.20. A turboprop engine according to claim 18, wherein said exhaust airguiding duct is arranged rearward of said heat exchanger.